Technology in connection with the exploration moreover production of hydrocarbon fluids, such as oil and gas, includes a variety of methods of drilling a wellbore into a formation to find and remove hydrocarbon fluids. During these drilling operations, drilling fluid is often pumped down through a drill pipe and into the wellbore through a drill bit, largely for the purposes of cleaning, lubricating, and cooling the drill bit. The drilling fluid mixes with sludge and cuttings (hereinafter referred to as “cuttings”), such as crushed rock and clay, before it is returned to the ground surface.
At the surface, the drilling fluid is typically separated from the cuttings and reused in the drilling process prior to disposal of the cuttings, especially when the drilling fluid includes oils or synthetic oils. However this separation at the rig site may be inefficient with typical rig site solids control equipment such as shale shakers, hydrocyclones and centrifuges, and a significant amount of drilling fluid may remain associated with the cuttings. In certain areas, the levels of oil that remain associated with the cuttings exceeds the levels allowed for discharge overboard or disposal at industrial landfills, and some form of secondary treatment is required.
Since the secondary treatment can not be done at the rig site with conventional equipment, in many cases the cuttings are collected at the rig site and transferred to a vessel such as a container, box, skip, or the like, that is then transported to a secondary drilling waste treatment facility, where the cuttings are emptied from the transport vessel. At this site further separation could be carried out using solvents, detergents, or thermal energy to reduce the oil levels on the cuttings to an acceptable level for disposal. An example of a drill cutting deoiling system is disclosed in United States Patent Application Publication No. 2005/0236015, which is incorporated herein by reference in its entirety. This secondary treatment site may be located within the drilling location or at another area. However, this involves unloading the cuttings and fluid from the transfer vessel either into a storage facility or directly into some kind of treatment vessel or unit. This transfer could require significant manpower and equipment. The transfer vessel is then cleaned and returned to the drilling site and refilled.
It can be appreciated that the large quantities of cuttings involved make it difficult, cumbersome, time-consuming, and expensive to transfer the mixture of fluid and cuttings to a vessel for transport to a treatment facility, then to empty the transfer vessel so it can be cleaned and returned to drilling site, and then to load the cuttings and fluids into the treatment process to reduce the oil content prior to disposal.
The present invention overcomes this problem.